Last Year's Petrol

[alanogden]

Two people have told me not to use last season's petrol in the mower. I can understand this with 2-stroke mixture but not a petrol engine surely?

[EDDIE51]

Only a problem if it has been in a moist area and water has got into it.
The water will be at the bottom but can get into the fuel tank if you tip the can right up to get all the petrol out.
Unless you drained the petrol tank of the mower at the end of last year then last seasons petrol will still be in it anyway.

[New Judge]

I always drain my mower's tank after every cut. However any petrol I have left over at the end of the season stays in a sealed can in the garage. I always use it in the following Spring (already started this year) with no problems.

[woofgang]

I keep mine from year to year and often leave petrol in the mower. The only way to drain it would be to turn the mower upside down or run it till its dry. touching wood I have never had a problem

[gingejbee]

I think that the rationale behind not using "old petrol" is that (particularly if it's got very warm/hot in storage) it could have lost lots of it's most volatile compounds....so the machine might be difficult/impossible to start and might run roughly, if you do get it to start.

[Old_Geezer]

Aye. I didn't realise the petrol 'went off' but apparently it does, and you may find it hard to start your mower and keep it running if your petrol is old. But I'd have thought 1 year wouldn't be that bad. Try it and see ?

[Maydup]

We sometimes get some new petrol and mix new with old to use it up. It won't really harm the mower, but best used up before long. I've never really known how to dispose of old petrol anyway, so have always kept stocks low and used up as soon as possible.

[Togo]

Leaded petrol will deteriorate if not stored in a sealed container.

//Stored petrol in a sealed container does not deteriorate, however as soon as you put it in a petrol tank feeding an engine it will start to go off. It does this as all tanks need to be vented to allow the petrol to be fed by gravity or a pump and as the petrol is used it needs to be replaced by air.
The low temp volatile fraction is the first to evaporate off.
In a modern fuel injected car this is normally not a problem as the injectors will have a fine enough spray for the mixture to ignite but in a carburettor this spells trouble, hence why on lawn mowers and classic cars and bikes you need to drain the petrol before the winter lay up.//

[Hopkirk]

Newspapers are always out of date. I can't see a future for the print versions.

[Togo]

Sorry I missed the link.

http://www.bishop-hill.net/discussion/post/2430730

[Hopkirk]

Oops wrong thread

[alanogden]

Thanks to all the contributors. I did start the mower on last year's petrol and it ran all right. The fuel was in a sealed plastic container all winter so it cannot have evaporated much.

[Khandro]

I had trouble starting my Honda mower last week with old petrol in the tank, it started but then died each time. (I had a thread on here about it). I eventually drained the tank and the carburettor, filled it with fresh 'super' and it ran fine.